One of the most significant developments in the field of liquid applications, including paints and other protective coatings, is the introduction and development of aerosolized coatings, most commonly referred to as an “aerosol can” or “spray paint.” In particular, low volatile organic content solvent-born coatings find use in the automotive and boating industry as sealers, basecoats, and clear coats. The coatings industry has expended much effort to reduce emissions of volatile organic solvents. In 1977 the Environmental Protection Agency (EPA) adopted its current policy for controlling emissions of volatile organic compounds (VOCs) based on photochemical reactivity. VOCs are typically known as any compound of carbon, excluding carbon monoxide, carbon dioxide, carbonic acid, metallic carbides or carbonates, and ammonium carbonate, which participates in atmospheric photochemical reactions.
The EPA now considers photochemical reactivity as one consideration when controlling organic solvent emissions to prevent ozone or smog formation. Because the paint and coatings industry is typically a heavy user of solvents, photochemical reactivity is an attribute to consider during development of formulations. Photochemical reactivity is a measure of how much a compound reacts in the atmosphere and contributes to the formation of ozone. It is a measure of the unique characteristics of a compound relative to its ability to form ozone. Reactivity is also affected by the characteristics of the atmosphere in which it reacts, so it is not just a function of the chemical itself. Other chemicals that may be present in the air, and the intensity of the sunlight, can affect the reactivity of a chemical. Reactivity is often used rather loosely to refer to the rate of ozone formation, the amount of ozone formed, or both.
All states have adopted regulations of VOCs based on calculations of Maximum Incremental Reactivity (MIR). An incremental reactivity (IR) calculated for a volatile organic mixture where the emissions of NOx (NO+NO2) have been adjusted to maximize the calculated MIR.IR=Δ[O3]/Δ[VOC]For a specified set of meteorological conditions, emissions, and initial concentrations, the incremental reactivity of an organic compound is the change in the peak ozone concentration, in grams, divided by an incremental change in the initial concentration and emissions of the organic compound.
In conforming to regulations regarding VOC emissions from paints and coatings manufacturers must also meet customer requirements of several critical properties including fast out-of-dust time, fast tack-up, good water resistance, good chemical resistance, sag resistance, and excellent appearance. Achieving these properties must be performed in a range of climates such as from hot and humid to cold and dry with each localities' ambient temperature (i.e. no baking).
Many high performance, high solids coating compositions in the art are based on polymeric systems comprised of either polyester-based or polyacrylic-based polyols and crosslinking agents. These coatings are generally supplied as two component or “two-pack” systems or “2K” systems. In a typical two-pack system, the crosslinking agent is combined shortly before application, with curing being conducted at ambient or elevated temperatures. While two pack systems often provide high performance properties like corrosion and humidity resistance, resistance to solvents, ultraviolet stability and gloss retention there are notable limitations.
Two-pack systems utilizing isocyanate crosslinkers require special handling and storage operations to prevent premature reaction with moisture and to avoid human exposure. Further, the components of two-pack systems can only be mixed shortly prior to use and once mixed must be used and ultimately be discarded. Another disadvantage of isocyanate-crosslinking systems is that the quality of the coating is compromised by bubble formation during thick film application. To avoid human exposure one company has developed a 2K system where a first container of “A components” is placed inside a second container containing “B components.” The A components could be a crosslinker that is necessary for reaction with the B components to form the final coating formulation. The first container can be ruptured to release the A components into the second container where they mix and react with the B components inside the second container. Alternatively, each container can be pressurized so that upon activation of a spray nozzle or valve will cause a stream of A components and B components to be expelled from both containers, mixed, reacted and applied to a substrate where it cures into a solid coating. These types of systems, however, are very expensive and difficult to manufacture.
My invention solves these problems and provides a new and improved liquid spray system that delivers an ambient curing, non-isocyanate coating formulation in an inexpensive container that is easily fabricated and is easy to prepare.